Modification of the Pet-Membrane/Solution Interface: Effect on Electrical Parameters

J. Benavente, R. de Lara*

Grupo de Caracterización Electrocinética y de Transporte en Membranas e Interfases

Departamento de Física Aplicada I. Facultad de Ciencias. Universidad de Málaga.

E-29071 Málaga (Spain)

 

 

Abstract

Electrochemical characterization of a symmetric track-etched polyethylenthereftalate (PET) membrane in contact with KCl solutions at different concentrations was carried out by measuring impedance spectroscopy (IS) and membrane potential (MP), which allow the estimation of membrane electrical resistance and ion transport numbers, respectively. IS measurements permit us the characterization of membranes in “working conditions” (in contact with electrolyte solutions) and the determination of electrical parameters for the membrane and the membrane/solution interface (resistance, capacitance and Warburg impedance) by analyzing the impedance plots and using equivalent circuits as models. The non-reproducibility of membrane potential values for two series of measurements and the asymmetry of the impedance curves show the modification of the membrane/aqueous solution interface. This point was confirmed by the time evolution of the membrane system electrical resistance and the increase of nitrogen content obtained from X-ray photoelectron spectroscopy (XPS) analysis for dry and PET samples maintained in water for different periods of time, and the results indicate an increase in nitrogen content, which is attributed to bacterial presence on the membrane surfaces. These results seem to indicate modification of the PET-membrane/solution interface due to fouling and the possibility of its determination by electrical measurements.

Keywords: PET-membrane; impedance spectroscopy, membrane potential, XPS

 

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* Corresponding author. E-mail address: J_Benavente@uma.es